1. Field of the Invention
The present invention relates to a light emitting diode, and more particularly, to a light emitting diode capable of uniformly emitting light of a desired color by converting wavelength of an intrinsic emission color of a light emitting diode chip.
2. Description of the Related Art
In general, a light emitting diode refers to a device that produces minority carriers (electrons or holes) injected by means of a p-n junction structure of a compound semiconductor and emits predetermined light due to recombination of the minority carriers. Since the light emitting diode has low power consumption and superior durability, the light emitting diode is applied to a variety of product fields. Further, light of a desired color can be emitted using a single chip or multiple chips.
For instance, in case of the single chip, red light can be emitted using a light emitting chip using GaAsP and the like, green light can be emitted using a light emitting chip using GaP and the like and blue light can be emitted using a light emitting chip using an InGaN/AlGaN double hetero structure.
In case of the multiple chips, white color can also be emitted by simultaneously using light emitting chips that emit red, green and blue lights. However, since the outputs of respective light emitting chips are changed depending on the ambient temperature when case that a specific color is implemented using a plurality of light emitting chips, the color coordinate can be changed. Further, different performance characteristics such as current and voltage requirements of the respective light emitting chips should be considered.
On the other hand, in case of the single chip, light of a desired color can be emitted using a light emitting chip of a compound semiconductor and a phosphor for converting the wavelength of primary light emitted from the light emitting chip.
For example, the blue light from the blue light emitting chip and the yellowish green or yellow light from the phosphor may be mixed by coating a blue light emitting chip with phosphor that emits yellowish green or yellow light using a portion of the blue light from the chip as an excitation source, so that a white color may be obtained. Further, an ultraviolet emitting chip is coated with a phosphor that absorbs the ultraviolet rays from the chip and emits visible light (from green to red), so that the ultraviolet rays can be converted into the visible light.
In general, the wavelength conversion of primary light from the light emitting diode can be obtained by injecting phosphors into epoxy used to fill a reflector cup. That is, liquid epoxy mixed with phosphor powder can be filled in a reflector or receptor mounted with a light emitting chip and then cured after a predetermined period of time. In addition, a light emitting diode can also be formed through a process of injecting the liquid epoxy mixed with phosphor powder into an injector and then potting a given amount of the liquid epoxy on a light emitting diode chip using a dispenser.
However, in a case where phosphor powder is mixed with epoxy, larger phosphor particles are settled down faster than smaller phosphor particles while the mixture is cured since the sizes of phosphor particles are not generally uniform. Thus, the concentration difference in liquid epoxy resin is generated due to the settlement of phosphors, and light emitted from the light emitting diode chip is not uniform. Therefore, there is a problem in color reproducibility and it is difficult to obtain uniform light of a desired color.
Furthermore, in order to prevent liquid epoxy resin from flowing to the sides, an additional receptor, reflector or protrusion is formed. Alternatively, liquid epoxy mixed with phosphor powder may be potted on a light emitting chip using a dispenser. However, since an additional manufacturing process is required, the process time and cost for the product manufacture is increased. Further, since an amount of the phosphor is not uniform when manufacturing the product, unstable colors are produced due the yield problem.
Recently, the light emitting diode products are not limited to display and backlight applications of a liquid crystal display and the like but are employed in the backlight applications of the liquid crystal display for use in electronic goods such as lightweight, thin, short and compact portable wireless telecommunication devices, automobiles and the like. Thus, the miniaturization is gradually needed. However, there is a problem in that the reduction in size of the conventionally manufactured light emitting diode products can be limited to a certain extent.